The present invention relates in general to vortex shedding flowmeter circuits and in particular to a new and useful circuit for processing the signal from a vortex shedding flowmeter which generates an analog and a pulse signal both of which are proportional to the output of the vortex shedding flowmeter sensor. This provides compatible outputs for connection to a digital control system without interface.
Vortex shedding flowmeters are known. In such flowmeters an obstruction or bluff is positioned in a fluid flow. Vortices are generated at alternate sides of the obstruction with a frequency which is proportional to the volumetric flow rate. The passage of the vortices thus is counted to provide a signal which indicates the flow rate.
Such a system is disclosed for example in U.S. Pat. No. 4,094,194 to Herzl.
It is also known to use a two wire transmission line for supplying power and receiving the signal from the vortex shedding flowmeter. Such a transmission line and arrangement is shown for example in U.S. Pat. Nos. 4,123,940 to Herzl et al and 4,134,297 to Herzl.
In prior art circuitry for processing the signal from a vortex shedding flowmeter, it has been necessary to provide an interface between the sensing equipment and digital control systems for processing the signal.